This invention relates to a catheter guide wire assembly and particularly relates to a core wire insertable in the assembly and to a distal tip configuration for that core wire.
In medical procedures such as angiography, a catheter must be positioned deep in the vascular system, and often such catheters must reach difficult to access regions. In order to introduce such a catheter into the vascular system of a patient, a sharp cannula is inserted through the skin and into the vascular system, and then a spring guide wire is inserted through the cannula. The cannula is then removed from the patient's body and the catheter is inserted into the body by sliding over the guide wire. The guide wire generally then is withdrawn, and the catheter is ready for further positioning and use. Catheters are also used in non-vascular procedures such as urinary tract procedures, and are introduced, as described above, with the aid of the catheter guide wire.
As used herein, the terms "catheter" and "guide wire" are meant to encompass all types of catheters and guide wires. For convenience, however, the specific example discussed herein relates to procedures dealing with the vascular system. The present invention is not limited to catheters and guide wires designed for the vascular system, and hence the benefits and advantages of the present invention apply equally to any medical procedure where a catheter must be feed through the skin and reach a remote location in the human body.
As stated earlier, the catheter guide wire assembly is inserted into the vascular system prior to the insertion of the catheter over the guide wire. The guide wire must be flexible and yet strong enough to negotiate the desired tortuous path of the vascular system and yet do no damage with its leading tip. Further, the guide wire must be strong enough to resist doubling back, kinking or breaking during the insertion and retraction processes.
Some catheter guide wire assemblies are one piece guide wire assemblies which include a wound outer casing with an ultra smooth surface and a safety core wire extending longitudinally within the casing and attached to each end thereof. This type of catheter guide wire assembly is described more fully in U.S. Pat. No. 4,003,369 by Heilman et al, the disclosure of which is incorporated herein by reference thereto. The core wire of the catheter guide wire assembly provides a degree of strength for the outer casing and appropriate rigidity such that the entire assembly can negotiate the vascular system. The flexibility of the entire guide wire assembly can be altered by changing the flexibility of the core wire at different longitudinal sections along the length thereof. In the Heilman et al patent discussed above, the core wire is tapered in a region proximate to its distal end to enhance its flexibility.
Due to the tortuous path the catheter guide wire assembly must take in the vascular system, and due to the need for selective rigidity and flexibility in the guide wire, a guide wire has been developed with a core wire insertable and movable within the catheter guide wire assembly. With an insertable core wire, the flexibility of the guide wire assembly at the tip can be altered by moving the core wire into and out of the region adjacent the distal end. Still, a great deal of skill is needed to guide the wire into the desired location in the vascular system, and to do so without damaging the vascular system itself. Also, with such a catheter guide wire assembly, care must be taken to minimize the possibility of the distal end of the core wire punching through the wound outer casing of the guide wire at the distal end thereof and also at other locations along the length of the guide wire assembly.